Whether your daughter likes it or not the infant child born to her shall be in her custody only.
You cannot decide about the custody of your child, it is the mother of the child who can make any decision about this.
Since he has suppressed the fact of his previous marriage and begetting children of the previous marriage, which wa material to the present marriage, your daughter can file a petition for annulling the marriage under section 12 of HMA.
She can claim maintenance or one time settlement for her daughter, she may not be eligible for maintenance for herself since she is employed and drawing salary as income.
Your daughter can lodge a criminal complaint against him for the offences of cheating mentioning the suppression of previous marriage details while marrying her and also for the cruelties meted out by him both physical and mental.
She can file a domestic violence case agaisnt him and can claim compensation for cheating her besides maintenance for her child.
Consult an experienced lawyer in the local who shall suggest more such measures and steps.